Chair

ABSTRACT

A chair includes: a seat body having a seating surface which provides seating to a user; a support device that supports the seat body such that the seat body is movable along a front-to-rear direction of the chair within a predetermined range; and an urging device. When the seat body is located in an area between a front position and a first reference position, the support device supports the seat body such that the seat body is moved to the front position by own weight. When the seat body is located between a rear position and a second reference position, the urging device urges the seat body toward the front position, whereas, when the seat body is located between the second reference position and the front position, the urging device does not urge the seat body.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2011-003150 filed on Jan. 11, 2011 in the Japanese Patent Office, thedisclosure of which is incorporated herein by reference.

BACKGROUND

This invention relates to a chair used in combination with a desk. Moreparticularly, the present invention is related to a chair configured soas to be movable (swingable) between a front position and a rearposition.

In a lecture room at school, for example, desks and chairs are disposedin alignment. Chairs used in such a place are configured so as to bemovable (swingable) between a front position and a rear position so thatpeople can easily move through between a desk and a chair. Specifically,the chair used in such a place is constituted in a manner that a seatbody, which provides seating to a user, can be moved rearward, when auser is seated, and the seat body can be moved to the front position,when nobody is seated.

Such chair is preferably configured in a manner that, when nobody isseated, the seat body is reliably located at the front position. Inorder to move the seat body to the front position, the chair is providedwith, in some cases, an urging device that urges the seat body of thechair, or that urges a support device supporting the seat body. However,in a chair provided with such urging device, when the seat body is movedto the front position, the seat body or the support device may collideagainst a stopper and the like, due to the urging force of the urgingdevice. The chair may be broken because of the shock of the collision.Or loud collision noise may be generated and gives an unpleasant feelingto a user and other people.

In order to solve this problem, a chair is suggested (see publicationsof Unexamined Japanese Utility Model Publication No. 05-21745 andUnexamined Japanese Patent Publication No. 2008-272456) wherein ashock-absorbing device is provided so as to restrict the speed of a seatbody moving to a front position. In such chair, the speed of the seatbody moving to the front position is restricted by the shock-absorbingdevice, such as a damper or a compression spring. Therefore, the shockgenerated when the seat body is moved to the front position can bereduced.

SUMMARY

In the above-described conventional chair, the urging device constantlyurges the seat body in a direction so as to move the seat body forward.Thus, even if a shock-absorbing device is provided, shock cannot besufficiently reduced in some cases. Moreover, there has been a problemin that, when the movement of the seat body from the front position tothe rear position is initiated, extremely large force is required so asto oppose the urging force.

A chair is preferably provided wherein the shock, generated when a seatbody is moved to a front position, can be reduced, and the seat body canbe easily moved.

The present invention, which is made in order to solve theabove-described and other problems, provides a chair including: a seatbody having a seating surface which provides seating to a user; asupport device that supports the seat body such that the seat body ismovable along a front-to-rear direction of the chair within apredetermined range; and an urging device.

When the seat body is located in an area between a front position, whichis a limit in a front side of the predetermined range, and a firstreference position, located behind the front position, the supportdevice supports the seat body such that the seat body is moved to thefront position by own weight.

When the seat body is located between a rear position, which is a limitin a rear side of the predetermined range, and a second referenceposition, located between the first reference position and the frontposition, the urging device urges the seat body toward the frontposition, whereas, when the seat body is located between the secondreference position and the front position, the urging device does noturge the seat body.

The position of the seat body may be understood as a position of acenter portion (center in the front-to-rear direction) of membersconstituting the seat body, or as a position of an entire portion of theseat body.

In the chair configured as above, when the seat body is located betweenthe rear position and the second reference position, the seat body isurged by the urging device and moved at least to the second referenceposition. In this case, the seat body can be located at the firstreference position, or in the front side of the first referenceposition. As a result, the seat body can be moved to the front positionby own weight. In other words, in the above-described chair, as long asthe seat body is free from external load, for example, manually pullingthe seat body and the like, the seat body can be automatically moved tothe front position.

The urging device stops urging the seat body, when the seat body ismoved into the front side of the second reference position. That is,when the seat body is moved to the front position, the seat body is nolonger under influence of the urging force of the urging device.Therefore, as compare to a case wherein the urging force is continuouslyapplied to a seat body until the seat body is moved to the frontposition, in the chair according to the present invention, shock thatcan be generated when the seat body is moved to the front position canbe reduced.

In the following, a case is considered wherein a seat body is moved fromthe front position to the rear position by, for example, manuallypulling the seat body. In order to start moving the seat body from astationary state of the seat body, larger force is initially required.That is because frictional coefficient becomes larger when the seat bodyis stationary. In addition, if urging force toward the front side isapplied to the seat body by the urging device, even larger force isrequired so as to start moving the seat body. However, in the chairaccording to the present invention, the seat body does not receive theurging force of the urging device in vicinity of the front position asdescribed above. Therefore, the present invention can inhibit the force,required so as to start moving the seat body, from being large. As aresult, the movement of the seat body can be smoothly and easilyinitiated.

One of the characteristics of the chair according to the presentinvention is that, when the seat body is located in the front side ofthe first reference position, the seat body can move to the frontposition by own weight. Own weight is not only the weight of the seatbody, but the weight of the support device supporting the seat body canbe also included. Being moved by own weight means that the seat bodymoves to the front position, and can also means that the support device,supporting the seat body, moves (makes motion) together.

The position of the second reference position may be substantiallyequivalent to the first reference position. The structure of the chairis required merely to be such that when the seat body is moved forwardfrom the rear position by the urging device, and reaches a positionwherein the seat body is no longer urged by the urging device, the seatbody is moved forward by own weight.

The urging device may be configured so as to urge the seat body bydirectly applying load, or by applying the load to the members connectedto the seat body.

Moreover, various ways may be adopted in order to achieve the structurewherein the urging force of the urging device is not applied to the seatbody when the seat body is moved in the front side of the secondreference position.

In one example, the urging device may include a pressing portion thatcomes in contact with and comes away from a predetermined surface of theseat body or of the support device. The urging device may be constitutedin such a manner that, when the seat body is located between the rearposition and the second reference position, the pressing portion comesin contact with the predetermined surface and presses the predeterminedsurface so as to urge the seat body toward the front position, and that,when the seat body is located between the second reference position andthe front position, the pressing portion comes away from thepredetermined surface so as not to urge the seat body. In the chairconstituted as above, when the seat body is moved in the front side ofthe second reference position, the pressing portion comes away from thepredetermined surface, and no longer presses the predetermined surface.Therefore, the seat body can be urged forward only when the seat body islocated in the back side of the second reference position.

The chair according to the present invention may include ashock-absorbing device that restricts moving speed of the seat bodytoward the front position.

According to this structure, the speed of the seat body moving to thefront position can be small due to the shock-absorbing device (forexample, a damper). Therefore, the shock that can be caused when theseat body is moved to the front position can be further reduced.

It is to be noted that the shock-absorbing device may be constituted soas to be able to restrict the moving speed of the seat body irrespectiveof the position of the seat body. The shock-absorbing device may beconstituted so as to restrict the moving speed of the seat body, forexample, throughout the movable range of the seat body, or only in onepart of the range. For example, if the shock-absorbing device worksbetween the rear position and the second reference position and themoving speed of the seat body is restricted, the shock, generated whenthe seat body is moved to the front position, can be reduced.

Moreover, the shock-absorbing device may be constituted so as torestrict the moving speed of the seat body toward the front position,only when the seat body is located in an area between the secondreference position and the front position.

In the chair constituted as above, the shock-absorbing device does notwork when the seat body is located in an area between the rear positionand the second reference position. In other words, in a state whereinthe seat body receives the urging force of the urging device, theshock-absorbing device does not work and the speed is not restricted bythe shock-absorbing device. Thus, the seat body can be smoothly moved tothe front position. On the other hand, when the seat body is located inan area between the second reference position and the front position,the shock-absorbing device works and the moving speed of the seat body,moving only by own weight, can be restricted in the vicinity of thefront position. Because the shock-absorbing device works in the vicinityof the front position under the situation wherein the seat body is movedonly by own weight, the shock that can be generated when the seat bodycomes to a stop can be extremely small.

The structure of the support device is not specifically limited, andvarious structures may be adopted.

In one example, the support device may include: a leg support installedon a floor surface; and a swing portion that supports the seat body andhas one end thereof connected to the leg support so as to be swingablein the front-to-rear direction around where the one end is connected.

In the chair constituted as above, the seat body can be moved by theswinging of the swing portion.

It is to be noted that the shape of the swing portion is notspecifically limited. Moreover, the swing portion may be constitutedwith one piece of columnar member, or with a plurality of columnarmembers.

Various members can be used as the urging device. In one example, theurging device may be a gas spring.

By using a gas spring as the urging device, the urging speed so as tourge the seat body can be easily and reliably controlled. That is, themoving speed of the seat body when the seat body is moved to the frontposition can be restricted and the shock can be reduced.

The chair according to the present invention may be configured asfollows: the urging device is a gas spring; the support device includesa leg support installed on a floor surface, and a swing portion thatsupports the seat body and has one end thereof connected to the legsupport so as to be swingable in the front-to-rear direction aroundwhere the one end is connected; the chair further includes a link armhaving one end connected to one end of the gas spring via a firstrotational shaft so as to be rotatable around the first rotationalshaft, and another end connected to the swing portion via a secondrotational shaft, disposed at a distance from the first rotationalshaft, so as to be rotatable around the second rotational shaft; anotherend of the gas spring is connected to a third rotational shaft, disposedin a position in which a distance from the second rotational shaftchanges corresponding to movement of the seat body, so as to berotatable around the third rotational shaft; and the gas spring may urgethe seat body to the front position by one of ways of extending andbeing compressed, when the seat body is located between the secondreference position and the rear position.

According the above-described construction, the swing portion swingsforward due to the gas spring extending or being compressed.Consequently, the seat body is moved forward (moved to the frontposition).

Moreover, the gas spring does not urge the seat body, when the seat bodyis located between the second reference position and the front position.Therefore, the shock that can be generated when the seat body is movedto the front position can be reduced.

Furthermore, one end of the gas spring is connected to the link arm. Thelink arm is connected to the swing portion. When the seat body is moved,the distance between the second rotational shaft and the thirdrotational shaft (to be also referred to as connection distance)changes. The above-mentioned connection distance can be changed evenwithout the gas spring extending or being compressed, because one end ofthe gas spring is connected to the swing portion via the link arm, andthe link arm is rotated with respect to the gas spring and the swingportion.

Therefore, when the seat body is moved between the second referenceposition and the front position, the connection distance can be changedwithout extending or compressing the gas spring. Due to this mechanism,the structure can be achieved wherein the gas spring does not urge theseat body when the seat body is located between the second referenceposition and the front position.

If one end of the gas spring is connected to the rotational shaft fixedto the swing portion and the gas spring is consistentlyextended/compressed corresponding to the movement of the seat body, theurging force of the gas spring is applied to the seat body whenever theseat body is moved irrespective of the position of the seat body.

The chair according to the present invention may be further providedwith a rotary damper disposed on at least one of the first and thesecond rotational shafts so as to restrict the moving speed of the seatbody toward the front position.

Due to this structure, the speed of the seat body when the seat body ismoved to the front position can be small by the shock-absorbing effectof the rotary damper. Therefore, the shock that can be generated whenthe seat body is moved to the front position can be further reduced.

The position of the rotary damper is not specifically limited. Moreover,an alternative shock-absorbing device other than the rotary damper maybe provided.

The chair according to the present invention may be constituted suchthat the swing portion is provided with an abutment surface pressed byone of the gas spring and the link arm when the gas spring extends. Dueto this structure, the gas spring can urge the seat body by pressing theabutment surface.

Furthermore, in the chair according to the present invention may beconstituted as follows: the urging device is a gas spring; the supportdevice includes a leg support, installed on a floor surface, and a swingportion having one end thereof connected to the leg support and anotherend thereof connected to the seat body so as to be swingable around theleg support; one end of the gas spring is engaged with an elongate hole,formed on the swing portion, so as to be slidable in the elongate hole;and another end of the gas spring is attached to a rotational shaft soas to be rotatable around the rotational shaft. The rotational shaft isdisposed in a position in which a distance from the elongate holechanges corresponding to movement of the seat body.

Due to this structure, the swing portion swings forward by the gasspring extending or being compressed. Consequently, the seat body ismoved to the front position. The gas spring does not urge the seat bodywhen the seat body is located between the second reference position andthe front position. Therefore, the shock that can be generated when theseat body is moved to the front position can be reduced.

Moreover, in the chair according to the present invention, one end ofthe gas spring is engaged with the elongate hole formed on the swingportion. When the seat body is moved, the distance between the elongatehole and the rotational shaft disposed on the other end of the gasspring (connection distance) changes. The connection distance can bechanged by one end of the gas spring sliding inside the elongate hole,without the gas spring extending or being compressed, because one end ofthe gas spring is engaged with the elongate hole.

Therefore, when the seat body is moved between the second referenceposition and the front position, the connection distance can be changedwithout extending/compressing the gas spring. As a result, the structurecan be achieved wherein the gas spring does not urge the seat body whenthe seat body is located between the second reference position and thefront position.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described below, by way of example, withreference to the accompanying drawings. However, it is to be noted thatthe embodiment described below is merely an example, and that thepresent invention can be carried out in various ways other than theembodiment explained below. In the drawings for the exemplaryembodiment:

FIG. 1 is a side view showing a chair according to an embodiment of thepresent invention;

FIG. 2 is a cross-sectional view showing a front leg and a rear leg ofthe chair according to the embodiment;

FIGS. 3A-3D are side views explaining movement of a seat body of thechair according to the embodiment;

FIGS. 4A-4B are side views showing a chair according to a variation ofthe present invention;

FIGS. 5A-5C are side views showing a chair according to anothervariation of the present invention;

FIGS. 6A-6B are side views showing a chair according to a furthervariation of the present invention;

FIGS. 7A-7B are side views showing a chair according to a yet anothervariation of the present invention; and

FIGS. 8A-8B are side views showing a chair according to a still furthervariation of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT (1) Entire Structure

As shown in FIG. 1, a chair 1 according to the present embodimentincludes a seat body 10, a leg support 20 installed on a floor surface,a front leg 30, and a rear leg 40. One ends (lower ends) of the frontleg 30 and the rear leg 40 are respectively connected to the leg support20, whereas the other ends (upper ends) thereof are respectivelyconnected to the seat body 10. The chair 1 is used in a place such as alecture room, in combination with a desk 2, and a plurality of suchcombinations is aligned in a front-to-rear and a left-to-rightdirections of the room. It is to be noted that in FIGS. 1 and 3-7, someportions of the chair 1 are shown with solid lines in order to clearlyshow the constituents of the chair 1, although these portions areactually hidden behind some other portions and cannot be seen.

The seat body 10 is provided with a seating surface 11 and a backrest12. In use of the chair 1, a user can manually pull (or lean on) thebackrest 12 rearward so as to move the seat body 10 away from the desk2, and be seated on the seating surface 11.

The seat body 10 is provided with a seat support 13 in a backside areaopposite to the seating surface 11. The seat support 13 is provided witha first shaft 14, connected to the upper end of the front leg 30, and asecond shaft 15, disposed behind the first shaft 14 (in the rightdirection in FIG. 1) and connected to the upper end of the rear leg 40.

The leg support 20 is provided with a third shaft 21, connected to thelower end of the front leg 30, and a fourth shaft 22, disposed behindthe third shaft 21 (in the right direction in FIG. 1) and connected tothe lower end of the rear leg 40.

The front leg 30 is configured in a manner such that one end thereof isrotatable with respect to the seat body 10 around the first shaft 14,and the other end thereof is rotatable with respect to the leg support20 around the third shaft 21. The rear leg 40 is configured in a mannersuch that one end thereof is rotatable with respect to the seat body 10around the second shaft 15, and the other end thereof is rotatable withrespect to the leg support 20 around the fourth shaft 22. Therefore, theseat body 10 is swingable in the front-to-rear direction.

FIG. 2 shows the cross-section cut along II-II in FIG. 1. The lateralcross-sectional surfaces of the front leg 30 and the rear leg 40 areformed nearly in U-shapes. The front leg 30 and the rear leg 40 aredisposed in such a manner that opening portions of the U-shapes face andloosely fit with each other.

Referring again to FIG. 1, in a space surrounded by the front leg 30 andthe rear leg 40, a gas spring 50 that urges the seat body 10 forward,and a link arm 52 are provided.

The gas spring 50 can be compressed by applying external force. When theexternal force compresses the gas spring 50, the gas spring 50 isprovided with constant repulsive force in a stretching directionopposite to the compressing direction. This repulsive force is generatedby fluid (gas) sealed inside of the gas spring 50. Depending on pressureand other factors of the gas sealed inside, force required forcompression, repulsive force to be generated, stretching speed and thelike of the gas spring 50 can be determined.

The link arm 52 is connected to one end (upper end) of the gas spring 50via a first rotational shaft 54 so as to be rotatable with respect tothe upper end of the gas spring 50. Moreover, the link arm 52 isconnected to the front leg 30 via a second rotational shaft 56, disposedin a position which is a predetermined distance away from the connectingposition of the link arm 52 and the upper end of the gas spring 50 (theposition of the first rotational shaft 54). The link arm 52 can berotated around the second rotational shaft 56.

The second rotational shaft 56 is provided with a rotary damper 58,which restricts rotational speed of the link arm 52 when the link arm 52is rotated with respect to the front leg 30 in a predetermineddirection.

The other end (lower end) of the gas spring 50 is connected to the rearleg 40 via a third rotational shaft 60 disposed on the rear leg 40. Thegas spring 50 can be rotated around the third rotational shaft 60.

Inside the front leg 30, a stopper block 62 is provided. Depending onthe position of the seat body 10, the stopper block 62 comes in contactwith, or comes away from the upper end of the gas spring 50 and the linkarm 52.

(2) Movement of Chair 1

The seat body 10 of the chair 1 is supported by the front leg 30, therear leg 40, and the leg support 20 so as to be movable (swingable) inthe front-to-rear direction. The change in the state of the seat body 10caused by the swing movement in the front-to-rear direction is shown inFIGS. 3A-3D. FIG. 3A illustrate a state wherein the seat body 10 ismoved rearward (to the right direction in FIG. 3) to a maximum extent(the state wherein the seat body 10 is located in a rear position). FIG.3D shows a state wherein the seat body 10 is moved forward (to the leftdirection in FIG. 3) to a maximum extent (a state wherein the seat body10 is located in a front position). The rear position may be theposition of the seat body 10 or the position of the chair 1, when a useris seated on the chair 1. The front position may be the position of theseat body 10 or the position of the chair 1, when nobody is seated onthe chair 1 and the chair 1 is moved to the closest proximity to thedesk 2.

The position of the seat body 10 may be understood as the position ofthe center portion (the center in the front-to-rear direction) of themembers constituting the seat body 10, or as the position of the entireportion of the seat body 10. In the present embodiment, the centerportion of the members constituting the seat body 10 is defined as theposition of the seat body 10.

Two drawings are further presented (see FIGS. 3B and 3C) and illustratethe state of the seat body 10 located between the rear position (FIG.3A) and the front position (FIG. 3D). When the seat body 10 is locatedin the front side of the seat body 10 shown in FIG. 3B, the seat body 10can be moved forward by own weight. The position of the seat body 10 orthe position of the chair 1 shown in FIG. 3B corresponds to the firstreference position according to the present invention. The firstreference position can be understood as a border (reference, in otherword) between the states whether or not the seat body 10 is movedforward by own weight. In the state shown in FIG. 3C, the forward urgingby the gas spring 50 with respect to the seat body 10 has finished. Theposition of the seat body 10 or the position of the chair 1 shown inFIG. 3C corresponds to the second reference position according to thepresent invention. The second reference position can be understood as aborder (reference, in other word) between the states wherein whether ornot the forward urging by the gas spring 50 with respect to the seatbody 10 has finished.

Rear positions, first reference positions, second reference positions,and front positions to be referred in variations, which will beexplained later, are respectively identical to the rear position, thefirst reference position, the second reference position, and the frontposition described above.

When the seat body 10 is located between the rear position (FIG. 3A) andthe second reference position (FIG. 3C), the seat body 10 is urgedforward by the urging force of the gas spring 50. In this case, unlessexternal force (for example, some force toward a direction opposite tothe direction of the urging by the gas spring 50) is applied to the seatbody 10, the seat body 10 can be moved at least to the second referenceposition (FIG. 3C). Moreover, when the seat body 10 is located betweenthe first reference position (FIG. 3B) and the front position (FIG. 3D),the seat body 10 can be moved forward by own weight as described above.

In the manner described above, the seat body 10 can be moved forward:only by the urging force applied by the gas spring 50 between the rearposition (FIG. 3A) and the first reference position (FIG. 3B); by theurging force of the gas spring 50 and the own weight between the firstreference position (FIG. 3B) and the second reference position (FIG.3C); and only by the own weight between the second reference position(FIG. 3C) and the front position (FIG. 3D). That is, unless externalforce (for example, some force urging the seat body 10 rearward) isapplied to the seat body 10, the seat body 10 is automatically moved tothe front position (FIG. 3D).

The following will describe this movement more in detail.

When the seat body 10 is located in the rear position (FIG. 3A), one end(the upper end) of the gas spring 50 is pressed by the stopper block 62,and the gas spring 50 is in a compressed state. The length of the gasspring 50 in this state is represented by L1, and the angle between thefloor surface and the lateral surface of the rear leg 40 is representedby θ1.

In order to keep the seat body 10 in the rear position (FIG. 3A), thegas spring 50 needs to be kept compressed by, for example, a usersitting on the chair 1. When the external load, applied in order to keepthe seat body 10 in the state at the rear position (FIG. 3A), is removedby, for example, the user getting up from the chair 1, the gas spring 50starts extending. The upper end of the gas spring 50 and the link arm 52press the stopper block 62. The gas spring 50 keeps extending until theseat body 10 passes the first reference position (FIG. 3B) and is movedto the second reference position (FIG. 3C).

The length of the gas spring 50 when the seat body 10 is located at thefirst reference position (FIG. 3B) is represented by L2, and the anglebetween the floor surface and the lateral surface of the rear leg 40 isrepresented by θ2. The length of the gas spring 50 when the seat body 10is located at the second reference position (FIG. 3C) is represented byL3, and the angle between the floor surface and the lateral surface ofthe rear leg 40 is represented by θ3. Moreover, when the seat body 10 islocated at the front position (FIG. 3D), the angle between the floorsurface and the lateral surface of the rear leg 40 is represented by θ4,and the length of the gas spring 50 becomes the same in FIG. 3C and FIG.3D. That is, the length of the gas spring 50 when the seat body 10 islocated at the front position (FIG. 3D) becomes L3. L3 is the length ofthe gas spring 50 when the gas spring 50 extends to the maximum extent.In other words, the stopper block 62 is not any further pressed by theupper end of the gas spring 50 from the state wherein the seat body 10is located at the second reference position (FIG. 3C). Therefore, therelation L3>L2>L1, and also the relation θ4>θ3>θ2>θ1 can be true.

Once the seat body 10 is urged by the gas spring 50 and moved to thesecond reference position (FIG. 3C), the seat body 10 can be movedforward by own weight. From the second reference position (FIG. 3C) tothe front position (FIG. 3D), the length of the gas spring 50 does notchange, and the link arm 52 is rotated around the first rotational shaft54 and the second rotational shaft 56. Consequently, the upper end ofthe gas spring 50 and the link arm 52 come away from the stopper block62.

The rotary damper 58, provided to the second rotational shaft 56, showsthe shock-absorbing effect after the seat body 10 is moved to the secondreference position (FIG. 3C). While the gas spring 50 and the link arm52 are in contact with the stopper block 62, the link arm 52 isdisplaced so as to maintain the same positional relation with respect tothe front leg 30 (see FIGS. 3A-3C), and is not rotated around the secondrotational shaft 56.

In other words, while the upper end of the gas spring 50 and the linkarm 52 are in contact with the stopper block 62, the rotary damper 58 isdisabled. When the upper end of the gas spring 50 and the link arm 52come away from the stopper block 62, the rotary damper 58 becomesfunctional.

The rotary damper 58 is constituted so as to show the shock-absorbingeffect only when the seat body 10 is moved forward, and not to show theshock-absorbing effect when the seat body 10 is moved rearward.Therefore, the seat body 10 can be moved to the front position (FIG. 3D)at restricted (controlled) speed. On the other hand, when the seat body10 is moved rearward, the moving speed of the seat body 10 is notrestricted by the rotary damper 58.

In order to move the seat body 10 from the front position (FIG. 3D) tothe rear position (FIG. 3A), external force that works toward the rearside of the seat body 10 needs to be applied by, for example, manuallypushing the seat body 10 rearward. Corresponding to the rearwardmovement of the seat body 10, the gas spring 50 and the link arm 52perform reverse movement opposite to the movement when the seat body 10is moved forward. That is, when the seat body 10 is moved from the frontposition (FIG. 3D) to the second reference position (FIG. 3C), the gasspring 50 does not extend or contract, but the link arm 52 is rotated.When the seat body 10 is moved from the second reference position (FIG.3C) to the rear position (FIG. 3A), the upper end of the gas spring 50contacts with the stopper block 62, and the gas spring 50 is pressed andgradually compressed.

(3) Effect of the Invention

In the chair 1 according to the present embodiment, the gas spring 50stops urging the seat body 10 when the seat body 10 is moved furtherfrom the second reference position (FIG. 3C) toward the front position(FIG. 3D). Therefore, the shock that can be generated when the seat body10 is moved to the front position (FIG. 3D) can be reduced.

Moreover, the rotary damper 58 restricts the moving speed of the seatbody 10 when the seat body 10 is moved beyond the second referenceposition (FIG. 3C) toward the front position (FIG. 3D). Therefore, theshock that can be generated at the front position (FIG. 3D) can befurther reduced. In addition, the rotary damper 58 does not restrict themoving speed of the seat body 10, until the seat body 10 is moved beyondthe second reference position (FIG. 3C) toward the front position (FIG.3D). Therefore, the seat body 10 can be smoothly moved to the frontposition (FIG. 3D).

Furthermore, in the chair 1, when the seat body 10 is located at thefront position (FIG. 3D), the urging force of the gas spring 50 is notexerted. In addition, the rotary damper 58 does not reduce the movingspeed when the seat body 10 is moved rearward. Thus, when the seat body10 is moved from the front position (FIG. 3D) to the rear position (FIG.3A) by, for example, manually pushing the seat body 10 rearward, theseat body 10 does not receive reaction force from the gas spring 50 andthe rotary damper 58 at the front position (FIG. 3D). As a result, theforce required to start the rearward movement of the seat body 10becomes small, and the seat body 10 can be smoothly moved rearward.

(4) Corresponding Relations

The front leg 30 and the rear leg 40 correspond to one example of theswing portion according to the present invention. One end (the upperend) of the gas spring 50 corresponds to one example of the pressingportion according to the present invention.

[Variation]

The above explained an embodiment of the present invention. However, itshould be understood that the present invention is not limited to theabove-described embodiment, and can be carried out in various wayswithin the technical scope of the present invention.

For example, in the above-described embodiment, one exemplary structureis presented wherein the upper end of the gas spring 50 and the link arm52 both contact with the stopper block 62. An alternative structure maybe adopted wherein only one of the upper end of the gas spring 50 andthe link arm 52 contacts with the stopper block 62.

Moreover, a structure without using the link arm 52 may be alsopossible. However, since the link arm 52 works so as also to restrictthe movable range of the gas spring 50 by being connected to the upperend of the gas spring 50, restricting the movement of the gas spring 50corresponding to the movement of the seat body 10 becomes difficult, ifthe link arm 52 is simply removed from the chair 1 according to theembodiment. Therefore, in the alternative structure, the movable rangeof the upper end of the gas spring 50 should be preferably controlled.For example, a structure as shown in FIGS. 4A and 4B may be adoptedwherein an elongate hole 64 is formed on the front leg 30, and anengaging piece 68, provided on one end of a gas spring 66, is engagedwith the elongate hole 64 so as to be slidable in the elongate hole 64.

FIG. 4A shows a state wherein the seat body 10 is located at a rearposition. FIG. 4B shows a state wherein the seat body 10 is located at afront position. The other end (lower end) of the gas spring 66 may beconnected to the rear leg 40 as shown in FIGS. 4A and 4B, or mayalternatively be connected to a constituent other than the rear leg 40.The gas spring 66 only needs to be attached so as to be rotatable arounda rotational shaft disposed in a position in which the distance from apredetermined position in the elongate hole 64 changes corresponding tothe movement of the seat body 10 (for example, the wall surface of theupper end of the elongate hole 64 (see FIG. 4A) on which the engagingpiece 68 abuts when the gas spring 66 extends, or the center point ofthe elongate hole 64, and so on). In the case of FIGS. 4A and 4B, theposition in which the other end (lower end) of the gas spring 66 isconnected may be arbitrary decided except on the front leg 30. The otherend (lower end) of the gas spring 66 may be attached to, for example,the leg support 20.

In a case wherein the elongate hole 64 is provided as described above,the elongate hole 64 may be formed in such a manner that the front leg30 is pressed by the engaging piece 68 contacting with an end portion ofthe elongate hole 64 as shown in FIG. 4A. That is, the end portion ofthe elongate hole 64 may be an alternative to the stopper block 62.

In the above-described embodiment, the structure is explained as anexample wherein the gas spring 50 is used as the urging device thaturges the seat body 10 forward. However, the urging device is notlimited to a gas spring, but various components may be alternativelyused. Moreover, the urging device may be attached in various positions.

A coil spring may be used as an urging device other than a gas spring.Moreover, in the above-described embodiment, a gas spring, which isextended by reactive force when the spring is compressed by applyingexternal force, is used as an example. Alternatively, a gas spring whichcontracts by reactive force when the spring is extended by applyingexternal force, may be used.

The disposition of a gas spring is not limited to the position in theabove-described structure, wherein one end (upper end) of the gas spring50 is connected to the front leg 30 via the link arm 52 and the otherend (lower end) of the gas spring 50 is connected to the rear leg 40.One end and the other end of a gas spring may be respectively connectedat various positions, for example, at any two points between which adistance to each other (the distance between the two points) changescorresponding to the movement of the seat body 10.

For example, in a case wherein the front leg 30 corresponds to the swingportion according to the present invention, rotational shafts may beprovided respectively to the front leg 30 and the seat body 10 (or theseat support 13 instead of the seat body 10), and a gas spring may beattached so as to connect the rotational shafts. The same applies to acase wherein the front leg 30 and the rear leg 40 correspond to theswing portion according to the present invention.

In a case wherein the front leg 30 and the leg receiver 20 correspond tothe swing portion according to the present invention, rotational shaftsmay be provided respectively to the rear leg 40 and the seat body 10 (orthe seat support 13 instead of the seat body 10), and a gas spring maybe attached so as to connect the rotational shafts. The same applies toa case wherein the rear leg 40 corresponds to the swinging portionaccording to the present invention.

In a case wherein the front leg 30 and the rear leg 40 correspond to theswing portion according to the present invention, rotational shafts maybe provided respectively to the rear leg 40 and the seat body 10 (theseat support 13), and a gas spring may be attached so as to connect therotational shafts. The rear leg 40 and the seat body 10 (the seatsupport 13), or the rear leg 40 and the leg receiver 20 may berespectively provided with rotational shafts, and a gas spring may beattached so as to connect the rotational shafts.

In the above-described embodiment, a structure is explained as anexample, wherein the moving speed of the seat body 10 is restricted bythe rotary damper 58 provided on the second rotational shaft 56.However, the rotary damper 58 may be disposed somewhere else other thanon the second rotational shaft 56. For example, the rotary damper 58 maybe disposed in the position of the first rotational shaft 54.Alternatively, other shock-absorbing device may be used instead of therotary damper 58.

Moreover, in the above-described embodiment, a structure is explained asan example, wherein the rotary damper 58 shows the shock-absorbingeffect between the second reference position (FIG. 3C) and the frontposition (FIG. 3D). However, the structure may be such that theshock-absorbing effect is shown when the seat body 10 is located at someother positions, for example, in the entire area between the rearposition (FIG. 3A) and the front position (FIG. 3D).

Various components may be used as the support device that supports theseat body 10. In the above-described embodiment, a structure isexplained as an example wherein the seat body 10 is supported by twolegs: the front leg 30 and the rear leg 40. Alternatively, the seat body10 may be supported by, for example, one leg. A chair 84, having a seatbody 82 supported by one leg 80, is shown in FIGS. 5A-5C. The seat body82 is provided with a seating surface 81 and a backrest 83. FIG. 5Ashows a state wherein the seat body 82 is located in a rear position.FIG. 5B shows a state wherein the seat body 82 is located at a secondreference position. FIG. 5C shows a state wherein the seat body 82 islocated at a front position. It is to be noted that a first referenceposition exists between the rear position (FIG. 5A) and the secondreference position (FIG. 5B).

In the chair 84, an upper end of a leg 80 is fixed to the seat body 82.A lower end of the leg 80 is pivotally supported by a leg support 86.Inside of the leg 80 is configured in a hollow state. Moreover, insidethe leg 80, a stopper block 88 and the gas spring 90 are disposed. Oneend (upper end) of the gas spring 90 is connected to the leg 80 via alink arm 92, and the other end (lower end) of the gas spring 90 isconnected to the leg support 86. A shock-absorbing device, such as arotary damper, may be provided.

In the chair 84 shown in FIGS. 5A-5C, the movement of the seat body 82is different from the movement of the seat body 10 of the chair 1 shownin the above-described embodiment (FIGS. 3A-3D). On the other hand, inthe chair 84, the same mechanism and effect as in the chair 1 can beachieved.

Moreover, a chair according to the present invention may be constitutedas a chair 100 shown in FIGS. 6A and 6B. The chair 100 includes a seatbody 110 which is provided with a seating surface 111 and a backrest112. In the chair 100, a front leg 102 may be fixed so as not to swing,and a rear leg 104 may be configured so as to swingable. In the exampleshown in FIGS. 6A and 6B, the front leg 102 is fixed almost in anupright standing state. FIG. 6A shows a state wherein the seat body 110(or the chair 100) is disposed at a rear position, while FIG. 6B shows astate wherein the seat body 110 (or the chair 100) is disposed at a rearposition. A first and a second reference positions exist between therear position (FIG. 6A) and the front position (FIG. 6B).

In the chair 100, a seat support 106 is provided with an elongate hole108 that engages with a shaft 102 a disposed in the upper end side ofthe front leg 102. Corresponding to the movement of the seat body 110,the shaft 102 a of the front leg 102 is relatively moved (slided) insidethe elongate hole 108. It is to be noted that an urging device may beprovided so as to urge the seat body 110 from the rear position to thesecond reference position. Moreover, a shock-absorbing device may beprovided so as to restrict the moving speed of the seat body 110.

Furthermore, a chair according to the present invention may beconstituted as a chair 120 shown in FIGS. 7A and 7B. FIG. 7A shows astate wherein a seat body 122 (or the chair 120) is disposed in a rearposition, while FIG. 7B shows a state wherein the seat body 122 (or thechair 120) is disposed in a front position. A first and a secondreference positions exist between the rear position (FIG. 7A) and thefront position (FIG. 7B).

The chair 120 includes the seat body 122 which is provided with aseating surface 123 and a backrest 124. The chair 120 may be configuredin such a manner that the seat body 122 is slidable in the front-to-reardirection on a supporting base 124.

Specifically, a bracket 125 is provided on a back surface of the seatbody 122. To the bracket 125, slide shafts 125 a and 125 b are secured.

On the supporting base 124, an elongate hole 130 is formed. The elongatehole 130 includes a horizontal portion 131 extending almosthorizontally, and an inclined portion 132 slanted so as to drop forward.

The slide shafts 125 a and 125 b engage with the elongate hole 130 so asto be slidable inside the elongate hole 130. As the slide shafts 125 aand 125 b slide inside the elongate hole 130, the seat body 122 can bemoved in the front-to-rear direction. Due to the inclined portion 132 ofthe elongate hole 130, the front end of the seat body 122 slantsdownward in the front position.

It is to be noted that, in FIGS. 7A and 7B, an urging device may beprovided so as to urge the seat body 122 forward up to the firstreference position where the seat body 122 becomes capable of movingforward by own weight. Moreover, a shock-absorbing device may beprovided in order to restrict the moving speed of the seat body 122.

A support device that support the seat body 122 may be disposed onsomewhere else other than a floor surface, for example, on a wallsurface, desk, and so on.

Although the above-described embodiment explained a structure as anexample wherein the stopper block 62 comes in contact with the gasspring 50 and the link arm 52, a structure without using the stopperblock 62 may be adopted. One example of a chair constituted in such amanner is illustrated in FIGS. 8A-8D.

The positions of a chair 130 are shown in the drawings, in the samemanner as the chair 1 illustrated in FIGS. 3A-3D, in which FIG. 8A showsa rear position, and FIG. 8D shows a front position. Between theabove-mentioned rear position (FIG. 8A) and the front position (FIG.8D), a first reference position (FIG. 8B) and a second referenceposition (FIG. 8C) are respectively determined from the rear side.

Since the chair 130 is not provided with a stopper block, the mechanismso as to compress the gas spring 50 is different from the mechanism ofthe chair 1.

The lower end 50 b (see FIG. 8A) of the gas spring 50 is connected tothe third rotational shaft 60, whereas the upper end 50 a (see FIG. 8A)is connected to the link arm 52 so as to be connected to the rotationalshaft 56 via the link arm 52. Therefore, when the distance between thesecond rotational shaft 56 and the third rotational shaft 60(alternatively, to be simply referred to as the above-describeddistance) is shortened by a predetermined value or larger, the gasspring 50 is rendered in the compressed state.

The above-described distance changes depending on the position of theseat body 10. When the seat body 10 is located at the rear position(FIG. 8A), the above-described distance becomes the shortest. Theabove-described distance becomes longer in the following order: when theseat body 10 is located at the first reference position (FIG. 8B); atsecond reference position (FIG. 8C); and at the front position (FIG.8D). That is, when the seat body 10 is located at the rear position(FIG. 8A), the gas spring 50 is in the most compressed state. When aseated person (a user) gets up, for example, and external load so as tokeep the seat body 10 at the rear position (FIG. 8A) is removed, the gasspring 50 extends, renders the above-described distance longer, and, asa result, urges the seat body 10 toward the first reference position(FIG. 8B). The gas spring 50 keeps extending until the seat body 10passes the first reference position (FIG. 8B) and reaches the secondreference position (FIG. 8C). The length of the extended gas spring 50becomes L3′>L2′>L1′.

When the seat body 10 is urged by the gas spring 50 and moved to thesecond reference position (FIG. 8C), the seat body 10 is moved forwardby own weight. Consequently, the above-described distance becomeslonger, but the length of the gas spring 50 does not change any more.Alternatively, the link arm 52 is rotated around the first and thesecond rotational shafts 54, 56 so as to follow the change in theabove-described distance. During this movement, the rotary damper 58shows the shock-absorbing effect.

In order to move the seat body 10 from the front position (FIG. 8D) tothe rear position (FIG. 8A), external force needs to be applied to theseat body 10 by, for example, manually pulling (or putting) the seatbody 10 rearward, in the same manner as the chair 1. As described above,the chair 130 can perform the same movement as the chair 1 shown inFIGS. 3A-3D.

Although a specific embodiment has been illustrated and describedherein, it is to be understood that the above description is intended tobe illustrative, and not restrictive. Combinations of the aboveembodiment and other embodiments will be apparent to those of skill inthe art upon reviewing the above description. The scope of the inventionincludes any other applications in which the above structures are used.Accordingly, the scope of the invention should only be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1. A chair comprising: a seat body having a seating surface whichprovides seating to a user; a support device that supports the seat bodysuch that the seat body is movable along a front-to-rear direction ofthe chair within a predetermined range; and an urging device, wherein,when the seat body is located in an area between a front position, whichis a limit in a front side of the predetermined range, and a firstreference position, located behind the front position, the supportdevice supports the seat body such that the seat body is moved to thefront position by own weight, and wherein, when the seat body is locatedbetween a rear position, which is a limit in a rear side of thepredetermined range, and a second reference position located between thefirst reference position and the front position, the urging device urgesthe seat body toward the front position, whereas, when the seat body islocated between the second reference position and the front position,the urging device does not urge the seat body.
 2. The chair according toclaim 1, wherein the urging device comprises a pressing portion thatcomes in contact with and comes away from one of the seat body and apredetermined surface of the support device, and wherein, when the seatbody is located between the rear position and the second referenceposition, the pressing portion comes in contact with the predeterminedsurface and presses the predetermined surface so as to urge the seatbody toward the front position, and when the seat body is locatedbetween the second reference position and the front position, thepressing portion comes away from the predetermined surface so as not tourge the seat body.
 3. The chair according to claim 1 further comprisinga shock-absorbing device that restricts moving speed of the seat bodytoward the front position.
 4. The chair according to claim 3, whereinthe shock-absorbing device restricts the moving speed of the seat bodytoward the front position, only when the seat body is located in an areabetween the second reference position and the front position.
 5. Thechair according to claim 1, wherein the support device comprises: a legsupport installed on a floor surface; and a swing portion that supportsthe seat body and has one end thereof connected to the leg support so asto be swingable in the front-to-rear direction around where the one endis connected.
 6. The chair according to claim 1, wherein the urgingdevice is a gas spring.
 7. The chair according to claim 1, wherein theurging device is a gas spring, wherein the support device comprises: aleg support installed on a floor surface; and a swing portion thatsupports the seat body and has one end thereof connected to the legsupport so as to be swingable in the front-to-rear direction aroundwhere the one end is connected, wherein the chair further comprises alink arm having: one end connected to one end of the gas spring via afirst rotational shaft so as to be rotatable around the first rotationalshaft; and another end connected to the swing portion via a secondrotational shaft, disposed at a distance from the first rotationalshaft, so as to be rotatable around the second rotational shaft, whereinanother end of the gas spring is connected to a third rotational shaft,disposed in a position in which a distance from the second rotationalshaft changes corresponding to movement of the seat body, so as to berotatable around the third rotational shaft, and wherein the gas springurges the seat body to the front position by one of ways of extendingand being compressed, when the seat body is located between the secondreference position and the rear position.
 8. The chair according toclaim 7 further comprising a rotary damper disposed on at least one ofthe first and the second rotational shafts so as to restrict movingspeed of the seat body toward the front position.
 9. The chair accordingto claim 7, wherein the swing portion comprises an abutment surfacepressed by one of the gas spring and the link arm, when the gas springextends.
 10. The chair according to claim 1, wherein the urging deviceis a gas spring, wherein the support device comprises: a leg supportinstalled on a floor surface; and a swing portion having one end thereofconnected to the leg support and another end thereof connected to theseat body so as to be swingable around the leg support, and wherein oneend of the gas spring is engaged with an elongate hole, formed on theswing portion, so as to be slidable in the elongate hole, and anotherend of the gas spring is attached to a rotational shaft, disposed in aposition in which a distance from the elongate hole changescorresponding to movement of the seat body, so as to be rotatable aroundthe rotational shaft.